The in vitro antimalarial activity of 17 ethanolic extracts and 15 basic alkaloid extracts obtained from eight plant species of the Apocynaceae family coming from the Loreto Region, was evaluated by flow cytometry. The strains used were: Plasmodium falciparum strain FCR-3 (resistant chloroquine) and strain 3D7 (sensitive chloroquine), cultivated by the methodology of Trager and Jensen with modifications. The P. falciparum DNA was stained with ethidium bromide for quantification by flow cytometry. Of the extracts tested, 15 were active inhibiting the growth of some of the strains of Plasmodium. The ethanolic extract of leaves of Odontadenia geminata showed the greatest activity against the strain FCR-3 (resistant chloroquine); and the alkaloidal extract of leaves of Malouetia tamaquarina against the strain 3D7 (sensitive chloroquine). Phytochemical screening revealed the presence of alkaloids, lactones and flavonoids, among other metabolites.